DAYS 1-5 (DECEMBER 13-17)
A temperature / dew point match and calm wind means that many wake up to a dense fog this morning, except portions of the South Coast where the temperatures are a little higher and there are only patchy areas of fog. Those areas are in the warm sector, while areas with the more widespread fog in place remained in the cooler air – i.e., the warm front never got through there. A frontal boundary from the west pushes through the region this morning and introduces a drier air mass to the region, which will be evident as fog dissipates and the wind picks up from the west during the day. But this air mass is not really that cold at all so it will be a nice day, temperature-wise. For areas in the cool air still, we call this frontal passage a “warm occlusion”, because the air behind the front from the west is milder than the air that was north of the warm front that did not make it through those areas. South of the warm front, areas that are in the warm sector will have that front pass as a cold front, though the air behind it will be milder as it passes those areas due to time-of-day, diurnal warming. Colder air will gradually filter into the region during tonight and we should have just enough clear sky to at least get a chance to view the peak of the Geminid meteor shower. This meteor shower can produce up to about 60 meteors per hour if you are viewing with clear sky and away from light pollution, so in our area the rate of visible meteors will likely be under that with at least partial cloud cover. The clouds come quickly back in overnight and into Monday while on the frontal boundary just gone by, a wave of low pressure will come rippling along rather quickly to the northeast. This low pressure area will come close enough to bring a period of snow and rain to the region during Monday, although it will be a fairly short-duration event that is not too heavy. It does have the potential to produce some minor accumulation of snow, and based on the track and marginal temperature profile expected, the greatest chance to see this accumulation will be along the I-95 and I-90 areas in general. This system exits Monday evening and a reinforcing cold front slides rather quietly through the region, but its impact will become rather noticeable as the cold air behind it arrives during Tuesday as high pressure to the north brings fair weather. This cold air is going to be around for a while, and plays a role in our next storm threat, currently timed for Wednesday night and Thursday. This will take place as low pressure tracks northeastward from lower Mississippi Valley toward the Ohio Valley, then quickly redevelops near the Mid Atlantic Coast, tracking just south of New England. The precise track of this low pressure area and the precipitation distribution to its north will determine how much snow falls in our area. With this threat at the end of our day 4 and well into our day 5 forecast, it’s far too soon to discuss specific snowfall amounts, but not too soon to say the system has the potential to produce a significant snowfall for at least a portion of the region. As always, this will be fine-tuned through the meteorological process as we get closer to the event, and you can see my thoughts in the daily comments section and of course each morning update.
TODAY: Widespread fog especially Boston area west and north to start, gradually dissipating toward midday. Mostly cloudy to partly sunny. Highs 55-62. Wind SW to W increasing to 5-15 MPH, gusts up to 25 MPH.
TONIGHT: Partly cloudy. Lows 28-35. Wind NW 5-15 MPH.
MONDAY: Mostly cloudy. A period of snow/mix/rain, but favoring snow with accumulations of a coating to 2 inches. Highs 32-39. Wind N to NW 5-15 MPH.
MONDAY NIGHT: Clearing. Lows 20-27. Wind NW 5-15 MPH.
TUESDAY: Mostly sunny. Highs 30-37. Wind N 5-15 MPH.
TUESDAY NIGHT: Mostly clear. Lows 17-24. Wind N under 10 MPH.
WEDNESDAY: Sun followed by increasing clouds. Highs 28-35 Wind N up to 10 MPH.
WEDNESDAY NIGHT: Thickening overcast. Snow arriving. Lows 18-25. Wind N to NE 5-15 MPH.
THURSDAY: Overcast with snow, ending late. Significant snow accumulation possible. Highs 23-30. Wind NE to N 10-20 MPH, higher gusts possible.
DAYS 6-10 (DECEMBER 18-22)
Dry, cold weather expected behind storm with Canadian high pressure December 18-19. Next unsettled weather threat comes later on December 20 with rain/mix/snow possible, followed by a return to dry weather December 21-22 and a shot of seasonably chilly air.
DAYS 11-15 (DECEMBER 23-27)
Pattern still looks somewhat active, a little milder to start, then colder again. Can’t rule out a couple rain/mix/snow threats which I’ll bring into focus as we get closer to this time period.